Compliant micro device transfer head array with metal electrodes
Compliant monopolar and bipolar micro device transfer head arrays and methods of formation from SOI substrates are described. In an embodiment, an array of compliant transfer heads are formed over a base substrate and deflectable toward the base substrate, and a patterned metal layer includes a metal interconnect layer electrically connected with an array of the metal electrodes in the array of compliant transfer heads.
1. A compliant micro device transfer head array structure, comprising:
a base substrate;
an array of compliant transfer heads formed directly over the base substrate and deflectable toward the base substrate, each compliant transfer head comprising:
a cavity into which the compliant transfer head is deflectable;
a lower insulating layer;
a spring layer directly over the lower insulating layer, wherein the spring layer includes a mesa structure protruding from a spring arm;
an upper insulating layer directly over the spring layer;
a first metal electrode directly over the upper insulating layer and the mesa structure
a second metal electrode directly over the upper insulating layer and the mesa structure, wherein the first metal electrode and the second metal electrode are electrically isolated from each other; and
a dielectric layer directly covering the first metal electrode and the second metal electrode directly over the mesa structure;
a second dielectric layer formed on walls of the cavity; and
a patterned metal layer including a first metal interconnect electrically connected with the first metal electrode for each said compliant transfer head and a second metal interconnect electrically connected with the second metal electrode for each said compliant transfer head.
2. The compliant micro device transfer head array structure of claim 1 , wherein each cavity is completely in the base substrate.
3. The compliant micro device transfer head array structure of claim 1 , wherein the first metal interconnect and the second metal interconnect are parallel to one another.
4. The compliant micro device transfer head array structure of claim 1 , further comprising a first and second through vias extending through the base substrate, and in electrical connection with the first metal interconnect and the second metal interconnect, respectively.
5. The compliant micro device transfer head array structure of claim 4 , further comprising an insulating layer covering a side surface of the first and second through vias.
6. The compliant micro device transfer head array structure of claim 5 , further comprising a first and second conductive layers on the passivation layer within the first and second through vias, and in electrical contact with the first metal interconnect and the second metal interconnect, respectively.
7. The compliant micro device transfer head array structure of claim 6 , wherein the first and second conductive layers do not completely fill the first and second through vias.
8. The compliant micro device transfer head array structure of claim 1 , wherein each cavity is a separate cavity.
9. The compliant micro device transfer head array structure of claim 1 , wherein the spring layer is a silicon layer.
10. The compliant micro device transfer head array structure of claim 9 , wherein the lower insulating layer is a silicon oxide layer.
11. The compliant micro device transfer head array structure of claim 1 , wherein the dielectric layer is formed of a high-k dielectric material.
12. The compliant micro device transfer head array structure of claim 1 , wherein the dielectric layer and the second dielectric layer are formed of the same material.
13. The compliant micro device transfer head array structure of claim 1 , wherein the mesa structure includes sidewalls.
14. The compliant micro device transfer head array structure of claim 13 , wherein the upper insulating layer of each said compliant transfer head is formed on the sidewalls and a top surface corresponding to the mesa structure of said compliant transfer head.